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Title: J-type Carbon Stars: A Dominant Source of 14 N-rich Presolar SiC Grains of Type AB

Here, we report Mo isotopic data of 27 new presolar SiC grains, including 12 14N-rich AB ( 14N/ 15N > 440, AB2) and 15 mainstream (MS) grains, and their correlated Sr and Ba isotope ratios when available. Direct comparison of the data for the MS grains, which came from low-mass asymptotic giant branch (AGB) stars with large s-process isotope enhancements, with the AB2 grain data demonstrates that AB2 grains show near-solar isotopic compositions and lack s-process enhancements. The near-normal Sr, Mo, and Ba isotopic compositions of AB2 grains clearly exclude born-again AGB stars, where the intermediate neutron-capture process (i-process) takes place, as their stellar source. On the other hand, low-mass CO novae and early R- and J-type carbon stars show 13C and 14N excesses but no s-process enhancements and are thus potential stellar sources of AB2 grains. And because both early R-type carbon stars and CO novae are rare objects, the abundant J-type carbon stars (10%–15% of all carbon stars) are thus likely to be a dominant source of AB2 grains.
Authors:
 [1] ;  [2] ;  [2] ;  [1] ;  [1] ;  [1] ;  [3] ;  [4] ;  [4]
  1. Carnegi Inst. for Science, Washington, DC (United States). Dept. of Terrestrial Magnetism
  2. Univ. of Chicago, IL (United States). Dept. of Geophysical Sciences; Chicago Center for Cosmochemistry, Chicago, IL (United States)
  3. Univ. of Chicago, IL (United States). Dept. of Geophysical Sciences.; Chicago Center for Cosmochemistry, Chicago, IL (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Nuclear and Chemical Sciences Division
  4. Univ. of Chicago, IL (United States). Dept. of Geophysical Sciences, Enrico Fermi Inst.; Chicago Center for Cosmochemistry, Chicago, IL (United States)
Publication Date:
Report Number(s):
LLNL-JRNL-732767
Journal ID: ISSN 2041-8213; TRN: US1800686
Grant/Contract Number:
AC52-07NA27344; NNX10AI63G; NNX15AF78G
Type:
Accepted Manuscript
Journal Name:
The Astrophysical Journal. Letters
Additional Journal Information:
Journal Volume: 844; Journal Issue: 1; Journal ID: ISSN 2041-8213
Publisher:
Institute of Physics (IOP)
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE; National Aeronautics and Space Administration (NASA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; 58 GEOSCIENCES; circumstellar matter; meteorites; meteors; meteorides; nucleosynthesis; abundances; stars: AGB and post AGB; stars: carbon; stars: dwarf novae
OSTI Identifier:
1414353